The present invention relates to devices used to prepare a bone to receive a prosthetic implant, and more particularly, to such a device used to prepare the proximal tibia to receive a proximal tibial implant.
The knee joint basically consists of the bone interface of the distal end of the femur and the proximal end of the tibia. Appearing to cover or at least partially protect this interface is the patella which is a sesamoid bone within the tendon of the long muscle (quadriceps) on the front of the thigh. This tendon inserts into the tibial tuberosity and the posterior surface of the patella is smooth and glides over the femur.
The femur is configured with two knob like processes (the medial condyle and the lateral condyle) which are substantially smooth and articulate with the medial plateau and the lateral plateau of the tibia, respectively. The plateaus of the tibia are substantially smooth and slightly cupped thereby providing a slight receptacle for receipt of the femoral condyles.
When the knee joint is injured whether as a result of an accident or illness, a prosthetic replacement of the damaged joint may be necessary to relieve pain and to restore normal use to the joint. Typically the entire knee joint is replaced by means of a surgical procedure that involves removal of the ends of the corresponding damaged bones and replacement of these ends with prosthetic implants. This replacement of a native joint with a prosthetic joint is referred to as a primary total-knee arthroplasty.
The surgical preparation of the patella, tibia and femur during primary total-knee arthroplasty is a complex procedure. A number of bone cuts are made to effect the placement and orientation of the prosthetic components on the bones with the appropriate joint gaps in extension and flexion. To resect the tibia, a cutting guide or block is mounted on the proximal tibia. The position, alignment and orientation of the cutting block are important for optimal performance of the prosthetic implant components. Generally, the tibial cutting block is positioned, aligned and oriented so that the cutting guide surface is in the optimal proximal-distal position, posterior slope, and varus-valgus orientation. A variety of alignment guides and cutting blocks have been provided in the prior art for use in preparing bone surfaces in primary total-knee arthroplasty, including alignment guides and cutting blocks used in preparing the proximal tibia.
Prior art alignment guides include the Specialist® 2 instruments (DePuy Orthopaedics, Inc., Warsaw, Ind.) for use with DePuy Orthopaedics' P.F.C.® Sigma Knee System. The tibial alignment guide for this instrument system includes an ankle clamp, a pair of telescoping alignment rods and a cutting block. Parts of this system are manually adjustable: the proximal-distal position of the cutting block is adjusted by sliding the telescoping rods and then locking the rods in the desired position; posterior slope is set at the ankle by sliding the distal end of the alignment rod in an anterior-posterior direction to thereby pivot the cutting block into the desired orientation; varus-valgus slope is set by pivoting the cutting block so that the alignment guide pivots about a rod at the ankle clamp. U.S. Pat. No. 6,090,114 discloses a tibial plateau resection guide. This system also uses an ankle clamp and extension rods to set the position and orientation of the cutting block. U.S. Pat. No. 5,451,228 also utilizes an ankle clamp but allows for angular orientation in the anterior-posterior plane to predetermined angular orientations using a thumb actuated slide mechanism; the device is however limited to predetermined angular settings. U.S. Pat. Nos. 6,685,711 and 6,595,997 disclose an apparatus and method for resecting bone that provides for aligning a resection guide in three degrees of freedom.